Eosinophilic gastrointestinal diseases, including eosinophilic gastroenteritis and eosinophilic esophagitis, commonly associated with food and aeroallergen hypersensitivity. Many of these patients have numerous food allergies, suggesting this disease entity represents an example of dysregulated mucosal tolerance. We are currently enrolling subjects in a clinical trial of omalizumab (therapeutic monoclonal anti-IgE) for eosinophilic gastroenteritis. The results of this study will yield information on the clinical utility of anti-IgE therapeutics in eosinophilic gastrointestinal diseases. Additionally, the results will provide data on the role of IgE mediated processes (immediate hypersensitivity, mast cell and basophil activation) in the pathogenesis of eosinophilic gastrointestinal diseases. Greater understanding of eosinophilic gastrointestinal diseases will provide a basis for future therapeutic strategies. Airway inflammation is central to asthma pathogenesis, and all guidelines for asthma therapy recommends anti-inflammatory therapy for all but the mildest asthma patients. Despite this, there are currently no clinically available non-invasive tests to measure airway inflammation in asthma. We currently are enrolling subjects in a clinical study utilizing exhaled breath condensate as a non-invasive technique to measure airway inflammation in pediatric patients. The results of this study will contribute to the development of non-invasive tools to measure and clinically manage asthmatic airway inflammation.